Ada County is by far the state’s largest in population, containing more than one quarter of the state’s residents, and contains its only county highway district; the Ada County Highway District (ACHD) has jurisdiction over all the local county and city streets, except for private roads and state roads. In the interior Northwest east of the Cascade Range, Ada County ranks second in population behind only Spokane County, Washington.

History

Ada County was created by the Idaho Territorial Legislature on December 22, 1864, partitioned from Boise County. It is named for Ada Riggs the daughter of H.C. Riggs, a member of the legislature which established the county and a co-founder of Boise.[5]Canyon County, which originally included Payette County and most of Gem County, was partitioned from western Ada County in 1891. Ada County Idaho Real Estate

Geography

According to the U.S. Census Bureau, the county has a total area of 1,060 square miles (2,700 km2), of which 1,053 square miles (2,730 km2) is land and 7.9 square miles (20 km2) (0.7%) is water.[6] The Boise River flows through the northern portion of the county, and the northwest border is bounded by the foothills of the Boise Range mountains, the summits are in adjacent Boise County. The southwestern border of the county is bounded by the Snake River. Ada County Idaho Real Estate.